Abstract: An apparatus for determining the depth of a tire tread includes a radiation source for illuminating the tread of a tire, the direction of the illumination being non-normal with respect to the local surface of a portion of a tire under inspection, at least one detector responsive to radiation reflected from the tire, and a data processor responsive to the at least one detector for calculating the tread depth. In one embodiment, differences in displacement between radiation reflected from the top surface of a tread and radiation reflected from the bottom surface of a tread are measured to determine tread depth. In a second embodiment, the shadow cast by the top surface of the tread over the bottom surface of the tread is measured to determine tread depth. A third embodiment employs a sheet of radiation with varying wavelength to determine the tread depth.